I know it is usually easier to go from an acyl chloride to an aldehyde,

but is there a way to synthesize acyl chlorides from an aldehyde?


Upon some textbook reading (Wiley: Organic Chemistry 11th Ed, Solomons), I realized that aldehydes could also be oxidized to carboxylic acids with chromic acid in aqueous acetone (the Jones Oxidation) and then you could react the carboxylic acid with thionyl chloride or phosphorus trichloride to yield the acyl chloride.

Another method was to convert the aldehyde into a cyanohydrin and through hydrolysis the -CN group could be then converted into $\ce{RCOOH}$. Then react $\ce{RCOOH}$ with $\ce{SOCl2}$ to get the acyl chloride.

  • 2
    $\begingroup$ If what you want is to convert RCHO to RCOCl, then I think your cyanohydrin method won't quite work. $\endgroup$ Dec 20, 2015 at 7:15

2 Answers 2


There are many ways to affect the transformation, as you have realised, and many of which Loong has detailed below in his post.

This answer gives one method which I would be confident of working practically, in the lab, using common reagents. A full search of Reaxys of SciFinder would reveal conditions/methods more suitable for a specific aldehyde.

A Pinnick oxidation will convert an aldehyde into its corresponding carboxylic acid, which may then be treated with a reagent such as oxalyl chloride to give the desired acyl chloride.

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In some cases, the direct reaction with chlorine is possible:

2-chlorobenzaldehyde and dichlorine to 2-chlorobenzoyl chloride
Clarke, H. T.; Taylor, E. R. o-Chlorobenzoyl chloride. Org. Synth. 1929, Vol. 9, 34; 1941, Coll. Vol. 1, 155.


In other reactions, radical chlorinating agents are used:

aldehyde and tert-butyl hypochlorite to acyl chloride
Ginsburg, D. The Action of t-Butyl Hypochlorite on Organic Compounds. II. Aromatic Aldehydes. J. Am. Chem. Soc. 1951, 73 (2), 702–704.


aldehyde and N-chlorosuccinimide to acyl chloride
Hebbelynck, M. F.; Martin, R. H. Bull. Soc. Chim. Belg. 1951, 60, 54.


aldehyde and sulfuryl chloride to acyl chloride
Arai, M. Bull. Chem. Soc. Jpn. 1962, 35, 1272; 1964, 37, 1280; 1965, 38, 252.


aldehyde and sulfuryl chloride to acyl chloride
Winstein, S.; Seubold, F. H. Jr. Free radical reactions of aldehydes. J. Am. Chem. Soc. 1947, 69 (11), 2916–2917.


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